This study will provide a detailed analysis of the surface ultrastructure of colonic epithelium from patients with chronic inflammatory bowel disease and adenocarcinoma using the scanning electron microscope. Ultrastructural correlates of colonic and rectal pre-cancer will be sought. Using transmission electron and light microscopy the junctional epithelia will be studied to obtain information about the nature of the interaction between malignant and normal tissues. Correlations with plasma and tissue carcinoembryonic antigen as well as the clinical course will be made.